Flip a boolean value without referencing it twice

Question

I am looking for a short syntax that would look somewhat like x *= -1 where x is a number, but for booleans, if it even exists. It should behave like b = not(b). The interested of this is being able to flip a boolean in a single line when the variable name is very long.

For example, if you have a program where you can turn on|off lamps in a house, you want to avoid writing the full thing:

self.lamps_dict["kitchen"][1] = not self.lamps_dict["kitchen"][1]

@norok2 The length. Either you can make it a one-liner and have to write the full name of `b` twice, or you can save a temp value beforehand and do `value = b; b = not value` which is even worse. — Guimoute, Sep 02 '20 at 11:10
You could use a temp variable differently, like `lamp = self.lamps_dict["kitchen"]; lamp[1] = not lamp[1]`. But I prefer Asocia's answer :-) — superb rain, Sep 02 '20 at 11:51
Related: [How to toggle a value in Python](https://stackoverflow.com/q/8381735/7851470). — Georgy, Sep 08 '20 at 16:44

score 13 · Accepted Answer · edited Feb 11 '21 at 14:13

13

You can use xor operator (^):

x = True
x ^= True
print(x) # False
x ^= True
print(x) # True

Edit: As suggested by Guimoute in the comments, you can even shorten this by using x ^= 1 but it will change the type of x to an integer which might not be what you are looking for, although it will work without any problem where you use it as a condition directly, if x: or while x: etc.

edited Feb 11 '21 at 14:13

dreamcrash

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answered Sep 02 '20 at 11:06

Asocia

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Flip a boolean value without referencing it twice

1 Answers1